Ruby
You can view our range of ethical rubies in our gemstone store. They are fully traceable, loose gemstones that have been responsibly sourced.
Rubies are often considered to be the most popular of the coloured gemstones, with their beautiful red colour being representative of love and passion, as well as a powerful energy for life. There are even mentions of ruby in the Bible.
The name “ruby” is given to gem material from the corundum family with a dominant red hue. Historically, some exceptional ruby was mined in the Mogok Valley in Myanmar (Burma) and Burmese ruby often commands a high price.
Ruby is a very hard gemstone, which is highly resistant to scratching. This means that it is perfect for daily wear in engagement rings. It has a rating of 9 on the Mohs Scale of Hardness (the same as sapphire) which makes it inferior only to diamond.
In Sanskrit, the word for ruby is ratnaraj, which means “king of gems”. It has been said that, if worn on the left hand, a ruby will bring good fortune to its wearer.
Burmese warriors had a belief that rubies could make them invincible in battle, but that they had to be inserted into their flesh to achieve that.
Ruby is a gemstone variety of the oxide mineral, corundum, comprising of the two elements, aluminium and oxygen, in a 2 to 3 ratio. These two chemical elements are required to form aluminium oxide (corundum) crystals. Ruby can range in colour from pink to deep red and it occurs when the corundum crystals contain small amounts of chromium, which act as a colouring agent.
One of the most common issues debated by gemmologists is what can be classified as a pink sapphire and when it becomes a ruby. Some trade organisations have defined the colour saturation at which this occurs, but it is often open to interpretation. Of course, most traders would like to call their stones rubies, as these usually command a higher price.
Historically, red spinel was often mistakenly called ruby, as these stones can look very similar and are sometimes found in the same mineral deposits. However, they can now be identified using some relatively simple gemmological tests. One of the most famous examples of this incorrect identification is the Black Prince "Ruby" in the British Imperial State Crown, which is actually a huge, red spinel.
Ruby is the birthstone for July.
Ruby Properties:
Refractive Index - 1.762 to 1.778
Birefringence - .008
Dispersion - .018
Optic Character - Uniaxial
Optic Sign - Negative
Specific Gravity - 4.00
Hardness - 9
Cleavage - Poor
Fracture - Conchoidal to Uneven
Lustre - Vitreous to Sub-adamantine
Transparency - Transparent to Opaque
As with sapphire, ruby is equally resistant to heat, light and chemicals (being the same material).
Corundum from Sri Lanka can include crystals of zircon, rutile (silk fingerprint) and also, garnet, mica, pyrite, ilmenite, kyanite and diaspore.
Sometimes there is a ‘star’ effect (asterism) present in rubies and sapphires (which are polished in the cabochon style to show the effect to best advantage). Like cat's eye (chatoyancy), the effect is due to fine parallel fibres or crystals (usually rutile, but sometimes hematite).
The host rocks for ruby and sapphire are dolomotized limestone, marble, basalt and pegmatite. Ruby is formed in metamorphic dolomite marbles, gneiss and amphibolite. Rubies and sapphires are often mined from secondary alluvial deposits rather than from the primary rock, with the vast majority of sapphires and rubies (thought to be over 80%) being produced by artisanal and small-scale mining (ASM) operations.
Some of the most well-known ruby producing countries are Sri Lanka (Ceylon), Madagascar (Ilakaka), Tanzania (Umba), USA (Montana) and Australia (Queensland). Historically, many impressive rubies were discovered in Burma (Myanmar), but the current leading producer for high-quality ruby is Mozambique.
Natural rubies and sapphires often contain a profusion of microscopically small canals or crystals, known as ‘silk’ that reflect the light and produce a whitish sheen, thereby detracting from the beauty of the gem material. Typically these crystals consists of rutile (titanium oxide).
Therefore a large percentage (some people quote up to 90%) of corundum is heat treated to improve the colour and clarity. This can be a very simple, relatively low temperature treatment using traditional blowpipe or other basic techniques. It could also be a gas or electric furnace with temperatures going as high as 1800C or more. The melting point for corundum is just over 2000C.
By heating the stones steadily and progressively through increasing temperatures over a period of hours or even days, it is possible to improve the overall clarity of rubies through the partial or complete dissolution of the rutile needles or intensify the colour of blue sapphires as the titanium is slowly diffused into the stone. This technique was used extensively and with great effect by gem traders from Thailand, who converted seemingly worthless "geuda" corundum from Sri Lanka into fine blue sapphires during the 1960s.
Of course, there is always a chance that heating can cause the ruby to crack or explode and, for that reason, heat treatment is usually performed on rough material rather than faceted.
After heat treatment, it is sometimes possible to see the so-called "snowball", "cotton ball" or "halo" effects caused by crystal inclusions or trapped gas bubbles expanding during the heating process. Whilst these can indicate possible heat treatment, they should not be considered as conclusive evidence.
The vast majority of rubies on the market today have been heat-treated in some way to improve their colour and clarity. Heat treatment in a gas or electric furnace is now a standard procedure in the gem industry.
Some of the best ruby in the world has originated in Burma (Myanmar). The term “Burmese” is often applied to outstanding examples of this gemstone, even when the stone itself did not come from that region.
View our range of rubies, all ethically sourced and fully traceable, in our gemstone store.